Audio 4:02
Growing tomatoes using evaporation and condensation

David Mark
Mon Feb 25 14:41:00 EST 2013

The one overriding factor limiting Australia's food production is the lack of fresh water. Given we have an abundance of space and light, solving the water problem opens up the possibility that Australia really could be the food bowl of Asia. A greenhouse in South Australia could provide one possible future - a way of growing fresh fruit and vegetables in the desert

Transcript

ELEANOR HALL: Australia's food industry benefits from an abundance of space and light. But an overriding factor limiting this arid country's food production is a lack of fresh water.

Now a greenhouse project in South Australia is pointing to evaporation and condensation as the answer to growing fresh fruit and vegetables in the desert.

David Mark has this report.

DAVID MARK: Around 20 years ago in Morocco on the edge of the Sahara, Charlie Paton had a revelation.

CHARLIE PATON: We were in a bus and it happened to be raining at the time and everybody in the bus was very wet because they'd been waiting for the bus to come. And as we travelled, the outside skin of the bus was being cooled by evaporation and it contained a large number of hot, damp people. And that resulted in a great deal of condensation forming on the windows of the bus.

And I thought there must be a window left open because it was running down, running along the floors.

DAVID MARK: What he was seeing was the process of evaporation and condensation. It's what happens when the hot moist air that forms when you have a shower condenses on a cold mirror.

Back on that bus in Morocco, Charlie Paton looked outside.

CHARLIE PATON: And I thought well, you know a place like Morocco that has this huge coastline of Atlantic coast and huge areas where it's impossible to grow things because it's too arid, there must be a way of using this effect to distil seawater.

DAVID MARK: He formed a company and eventually helped build a greenhouse just 100 metres from the sea at Port Augusta in South Australia that's now used to grow tomatoes.

The seawater is pumped to the greenhouse and evaporated to form fresh water and then another simple process kicks in - evaporative cooling.

CHARLIE PATON: What we do with the greenhouse is we have an entire wall that faces the prevailing wind covered with an evaporator material and we pour seawater over it so that the air that comes through that wall is made much more humid and at the same time much cooler.

DAVID MARK: In other words, the tomato plants inside the greenhouse don't need as much water as they would if they were outside.

CHARLIE PATON: Every litre, every drop of water we evaporate actually has a beneficial effect.

DAVID MARK: Australia is largely an arid country, the amount of land that's useful for agriculture is actually relatively small. What sort of potential is there in a country like Australia for this sort of technology?

CHARLIE PATON: Australia has the most ideal conditions in many ways, because you've got so much light. So where you have high levels of solar radiation, you've got potential to grow large volumes of biomass of crop. The limiting factor is water, but even so there is - Australia has a great deal of coast and there's no shortage of seawater.

DAVID MARK: There's no shortage of seawater in Australia but there is a shortage of good quality soils. How do you get around that problem?

CHARLIE PATON: Commonly now in a commercial greenhouse, you don't use soil at all. All commercial greenhouses now use, well nearly all of them use a process called hydroponics, where you add the nutrients to the water and it's a very much more efficient method of optimising the crop, and also eliminating problems of pest and disease, because you can take pure, clean, sterilised water and add exactly the nutrients that the plants are going to need.

And there is zero wastage of water.

DAVID MARK: The population in our region around Asia is expanding rapidly. What is the role of technology in food production?

CHARLIE PATON: Conventional farming has obviously got to change, I mean I think it's true to say that quite a number of the problems to do with water and the whole water budget in Australia are to do with farming practices that are no longer viable and any method of evaporating seawater has a positive, beneficial effect to the country because it's water that's in short supply.